REF. : FBLS.01.BC.17R1 / FBLS.01.BC.18R2 / FBLS.01.BC.19R3 / FBLS.01.BC.20R3 / FBLS.01.BC.21R1 The clasps FBLS.01. BC.17R1 and FBLS.01. BC.18R2 have a spring assisted closure. The second model is optimized (the spring is a simple blade). FBLS.01. BC.19R1 and FBLS.01. BC.20R1 are also spring loaded. Additional parts (which make the blockage) require heat treatment. The blade must have the same hardness to avoid wear. The FBLS.01. BC.20R1 needs security (for example in 8).